<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<style type="text/css">
/* id选择器 */
  #d1{
  color: red;
  }.c1{
  color: green;
  }
  /* 分组选择器 */
  #d1,.c1,li{
  background-color: green;
  }
  /* 属性选择器 */
  input[type='password']{
  background-color: purple;
  }
</style>
</head>
<body>
<p>p1</p>
<p id="d1">p2</p>
<p class="c1">p3</p>
<h3>h3_1</h3>
<h3>h3_2</h3>
<h3 class="c1">h3_3</h3>
<ul>
  <li>li-1</li>
  <li>li-2</li>
  <li class="c1">li-3</li>
</ul>
<input type="text">
<input type="password">
</body>
</html>